[P-PS06] Lunar Science and Exploration

[PPS06-01] Lunar Impact Flash Observing Mission by 6U Spacecraft EQUULEUS (1): Mission Summary and Initial Results

★Invited Papers

*Shinsuke Abe¹, Masahisa Yanagisawa², Ryota Fuse³, Satoshi Ikari³, Masahiro Fujiwara³, Hirotaka Kondo³, Jungo Okuyama¹, Kazuhide Komai¹, Hajime Yano⁴, Masaki Tsutsui³, Akihiro Ishikawa³, Yosuke Kawabata³, Shintaro Nakajima³, Kota Miyoshi⁴, Ryu Funase^4,3 (1.Nihon University, 2.University of Electro-Communications, 3.The University of Tokyo, 4.The Japan Aerospace Exploration Agency/The Institute of Space and Astronautical Science)

Keywords:Lunar impact flash, Meteoroids, Solar system small bodies, 6U Spacecraft

A fireball is a bright meteor caused by a centimeter-sized meteoroid and is a rare phenomenon from a ground-based observation. The Lunar Impact Flash (LIF) observation uses the large lunar surface as a telescope to detect meteoroids larger than centimeters, which is about 100 times more efficient than a single ground-based observation on Earth. In other words, LIF observation is a new tool to investigate the size distribution, collision frequency, and seasonal and temporal variations of meteoroids which can reveal the unknown Earth-Moon impactors ranging between meteors and asteroids. However, a long-term continuous LIF observation from the ground is difficult due mainly to the limitation of the lunar phase and weather conditions. Thus the LIF observation from a Lunar Orbital Platform Gateway or around the Earth-Moon Lagurangeun Point L2 can be strongly proposed. Also, the LIF observation can be used for the environmental monitoring of lunar impactors for human activities on the Moon.

Through the lunar impact flash observations, we will be able to (1) clarify the size and mass distribution functions and impact frequency of meteoroids sizing between centimeters and several tens of centimeters, (2) explore the internal structure of the Moon by collaborating with moonquake measurements, (3) search for new craters related with LIF events and better understanding the physics of celestial hypervelocity impacts. It can also be used to evaluate the affected region by impact ejecta and to confirm the impact site by artificial space debris in the future.

"EQUULEUS" is a 6U CubeSat developed by the University of Tokyo and JAXA, which will fly to a libration orbit around the second Earth-Moon Lagrange Point (EML2) as a piggy-back payload of NASA's Space Launch System (SLS). The lunar impact flash observing camera "DELPHINUS" onboard EQUULEUS, developed in collaboration with Nihon University, the University of Electro-Communications, the University of Tokyo, JAXA, and major manufacturers, has been launched on November 16, 2022, as one of the secondary payloads of NASA Artemis 1 SLS and successfully detached from the SLS on the way to the moon. After the checkout operation and the first light imaging, the camera successfully took a series of images of the far side of the moon during the lunar flyby.

This paper describes the mission summary of the lunar impact flash observing camera onboard 6U Spacecraft EQUULEUS and also reports on the performance evaluation comparing the images obtained so far and data obtained from ground tests, and introduces the future mission schedule and expected results.